1. Field of the Invention
The present invention relates to an electrically rewritable nonvolatile semiconductor memory device, and a system thereof.
2. Description of the Related Art
A conventional flash memory has a digital control interface. Then, in addition to a digital control signal terminal, the flash memory has a power source terminal, and a writing and erasing power source terminal. These are DC inputs, which are controlled in accordance with a digital control signal from the outside inside of the flash memory to be rectified into an appropriate waveform and applied to a memory cell. As a consequence, a large number of control circuits which are referred to as peripheral circuits are provided in addition to the memory cells in order to create a signal required for the reading, writing, and erasing of the memory cell inside of the flash memories.
Conventionally, a large number of peripheral circuits are formed in a chip for creating a signal required for the reading, writing, and erasing of the memory cell inside of the flash memory with the result that the chip size is enlarged and a cost thereof is increased. However, when an attempt is made to directly control the memory cell from the outside, an outside wiring load is increased.
Furthermore, conventionally, a large number of detachable memory devices are provided which use a flash memory. For example, a smart medium, a compact flash, a memory stick, an SD card or the like is provided. An interface of the smart medium is the interface itself of a NAND flash memory. Other devices are similar to the interface of a magnetic storage device. In any way, like the magnetic memory device, file data and a logical address are received and memorized under the file control on the host side. A file control system is required on the host side.
In this manner, the conventional memory device using the flash memory is controlled under the file control on the host side, so that the performance thereof is deteriorated. For example, when the minimum rewriting unit of the flash memory is larger than the minimum unit of the file control on the host side, it is required to rewrite even the file data which is not required to be rewritten inside of the flash memory at the time of rewriting one piece of file data. However, when an attempt is made to conduct the file control on the side of the flash memory system, there arises a problem as to how the interface is dealt with.